class_docstr: BatchNorm2d where the batch statistics and the affine parameters are fixed.
  
  It contains non-trainable buffers called
  "weight" and "bias", "running_mean", "running_var",
  initialized to perform identity transformation.
  
  The pre-trained backbone models from Caffe2 only contain "weight" and "bias",
  which are computed from the original four parameters of BN.
  The affine transform `x * weight + bias` will perform the equivalent
  computation of `(x - running_mean) / sqrt(running_var) * weight + bias`.
  When loading a backbone model from Caffe2, "running_mean" and "running_var"
  will be left unchanged as identity transformation.
  
  Other pre-trained backbone models may contain all 4 parameters.
  
  The forward is implemented by `F.batch_norm(..., training=False)`.
code: def _load_from_state_dict(
      self,
      state_dict,
      prefix,
      local_metadata,
      strict,
      missing_keys,
      unexpected_keys,
      error_msgs,
  ):
      version = local_metadata.get("version", None)
  
      if version is None or version < 2:
          # No running_mean/var in early versions
          # This will silent the warnings
          if prefix + "running_mean" not in state_dict:
              state_dict[prefix + "running_mean"] = torch.zeros_like(
                  self.running_mean
              )
          if prefix + "running_var" not in state_dict:
              state_dict[prefix + "running_var"] = torch.ones_like(
                  self.running_var
              )
  
      super()._load_from_state_dict(
          state_dict,
          prefix,
          local_metadata,
          strict,
          missing_keys,
          unexpected_keys,
          error_msgs,
      )
  
imports: import torch
  import torch.distributed
  from fvcore.nn.distributed import differentiable_all_reduce
  from torch import nn
  from torch.nn import functional
  from detectron2.utils import comm, env
  from .wrappers import BatchNorm2d
label_desc: Use image node_id 3 for calling the FrozenBatchNorm2d obj's underlying member method code with example usage: obj._load_from_state_dict(state_dict, prefix, local_metadata, strict, missing_keys, unexpected_keys, error_msgs) without return types